On Wed, 2008-02-27 at 21:03 -0500, Mark Rodriguez wrote:
> James,
>
> > When doe s the error occur?
> > 0. When program starts
> > 1. When shutting down
> > 2. When creating the text_view the first time
> > 3. When creating the text_view the Nth time
> >
> > I will assume it happens durin shutdown (#1).
>
> Yes you are correct. In the "real" application, the application
> doesn't exit. It destroys the canvas and re-uses it with new controls.
> Rather than debug that [monster], I reduced the application to
> something more manageable that exhibit the same behavior.
>
> > Yes, it should be handled like any other widget. The only special thing is
> > its text_buffer! Consider gtk_text_view_new_with_buffer(), one is created
> > automatically for when using the gtk_text_view_new() api. I don't think
> > creating the GtkTextBuffer first would make any difference -- however, that
> > where you are now. So try creating the GtkTextBuffer first, then use the
> > ...with_buffer() api to create the view. This may produce a different
> > result.
>
> Interesting. I tried a few different things today and was able to get
> the application to work as expected without crashing, but I don't like
> the solution as now it appears I'm leaking memory. Any thoughts on why
> if g_object_unref is called the application complains about the double
> free? I modified the code as follows (mainly the button_click_event
> handler was changed to handle the text buffer and to require clicking
> the 'Quit' button twice for exiting the app - this was just done for
> visibility reasons).
>
ref's are strange things: When I run into this anomaly I do the
following, reasoning that I must have only had a weak reference, and
g_object_unref got confused -- anyway this normally works for me.
/* creation code ... */
...
buffer = gtk_text_buffer_new(NULL);
if (buffer != NULL) {
g_object_ref (G_OBJECT(buffer));
gtk_object_sink (G_OBJECT(buffer));
}
sinking it ensures that you have a full fledged reference that a later
unref will honor.
If your creating and deleting this text_view as needed, you will have to
find the root cause of these messages. I notice that you prep'ed the
main() to use threads. Your problem maybe related to how your using
threads when creating/destroying the text view. I would suggest
exploring this type of change.
1a. Only create/destroy in the main gtk/gdk thread.
1b. Fire off a g_timeout_add( 500000, (GSourceFunc)fn_create_routine(),
gpointer); where "gboolean fn_create_routine(gpointer gp);" calls the
normal gtk_window_new() stuff to create a dialog or the window you plan
to use the text_view in. All this gets you out of the normal gtk signal
chain of events. signals iterate on themselves and I've seen unwinds
cause random errors - like your double-free.
1c. Do essentially the same to destroy the window.
2a. I guess I don't actually delete/destroy main windows once created, I
just hide them and present them again when needed.
2b. Or if I do destroy them, i keep the buffer and/or tree_model in a
allocated memory structure. Thus gtk_text_view_new_with_buffer() is the
type of call I most often use to create text_views.
3. You seem to be _show() ing objects before adding them to something.
Look at vbox; you create it, show it, then add it to the main.window.
The recommended style is to create, add, show. I don't think causes
any immediate problems but it could be polluting something- anyway this
strikes me as something worth cleaning up.
James,
> [code]
> GtkWidget *main_window, *text_view, *box, *button;
> GtkTextBuffer* buffer;
>
> static void destroy_event(GtkWidget* widget, void* data)
> {
> gtk_main_quit();
> }
>
> static void button_click_event(void)
> {
> if (text_view != NULL)
> {
> gtk_container_remove(GTK_CONTAINER(box), text_view);
> text_view = NULL;
> // leaking memory???
> // g_object_unref(G_OBJECT(buffer));
> buffer = NULL;
> }
> else
> {
> gtk_widget_destroy(main_window);
> main_window = NULL;
> }
> }
>
> int main(int argc, char* argv[])
> {
> // initialize multi-threading within GLib
> g_thread_init(NULL);
>
> // initialize multi-threading within GDK
> gdk_threads_init();
>
> // acquire thread lock
> gdk_threads_enter();
> gtk_init(&argc, &argv);
>
> // create main window
> main_window = gtk_window_new(GTK_WINDOW_TOPLEVEL);
> if (main_window == NULL)
> abort();
> g_signal_connect(G_OBJECT(main_window), "destroy",
> G_CALLBACK(destroy_event), NULL);
> gtk_widget_show(main_window);
>
> box = gtk_vbox_new(FALSE, 5);
> if (box == NULL)
> abort();
> gtk_widget_show(box);
> gtk_container_add(GTK_CONTAINER(main_window), box);
>
> buffer = gtk_text_buffer_new(NULL);
> if (buffer == NULL)
> abort();
>
> text_view = gtk_text_view_new_with_buffer(buffer);
> if (text_view == NULL)
> abort();
> gtk_widget_show(text_view);
> gtk_box_pack_start(GTK_BOX(box), text_view, TRUE, TRUE, 5);
>
> button = gtk_button_new_with_label("Quit");
> if (button == NULL)
> abort();
> g_signal_connect(G_OBJECT(button), "clicked",
> G_CALLBACK(button_click_event), NULL);
> gtk_widget_show(button);
> gtk_box_pack_start(GTK_BOX(box), button, TRUE, TRUE, 5);
>
> // run the main loop
> gtk_main();
>
> // release thread lock
> gdk_threads_leave();
>
> return 0;
> }
> [/code]
>
>
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